Is there a formal notation for a set of quantiles of for instance x, a numerical array? This answer suggests the notation for percentile is Pi (though what to do if you already have a variable P is unclear - I presume to use Q). But how to represent a set? Strictly speaking can it be a set if two quantiles share the same value? I'm unclear if/how the notation for an array would apply here. A steer would be much appreciated.
I do note this from Wikipedia:
But this seems aimed at identifying the "k-th" quantile.